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Pelagites and Organic-Rich Sediments |
Grant Institute of Geology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, Scotland, U.K.
BP, Britannic House, Moor Lane, London, UK
The Miocene Salir Formation in SW Turkey is a 500 m thick dominantly terrigenous clastic succession deposited by turbidity currents and other mass-flow mechanisms on a series of small submarine fans. During intervals of non-clastic deposition hemipelagic chalk horizons up to 60 mm thick accumulated.
The chalks comprise disseminated planktonic and small benthonic foraminifera dispersed in a micrite matrix with abundant poorly preserved coccolith plates and other nannoplankton fragments. Biogenic sand and silt-sized particles form up to 20% of the rock. Carbonate content ranges from 55% to 95%. The non-carbonate component comprises dispersed clay platelets and in some beds silt-sized particles. The chalks range from structureless homogeneous units, to beds which show a wide range of sedimentary structures which suggest reworking of the slowly deposited hemipelagic ooze by bottom currents of fluctuating velocity.
The lateral and vertical distribution of the hemipelagic chalks reflects the area on the submarine fan on which they were deposited. Areas away from the main locus of deposition, for example interchannel areas in proximal sequences, and inactive mid-fan areas are characterized by frequent and often thick chalk beds. In active mid-fan and inner-fan channel areas hemipelagic chalks are scarce or absent.
